1. Field of the Invention
The invention relates to an apparatus for determining the cross sectional shape and area of an elongated wire or cable-like product. The invention also relates to a method for determining the cross sectional shape and area of the elongated wire or cable-like product using the inventive apparatus.
2. Description of Prior Art
Continuous, in-line rolling of steel wire rod, or other wire or cable-like products, in a high speed mill is a process which is controlled by maintaining strict control of the cross sectional area of the product at various points in the process. Because of speed, access and environmental limitations, a continuous measurement of the cross sectional area is not feasible. Accordingly, the process is controlled statistically by taking samples of the product in process in a controlled fashion. The cross sectional area of the samples are measured and statistical methods are used to determine process corrections.
Samples taken for this purpose are approximately 30 cm long and typically have an irregular cross sectional shape. Proper process control demands frequent sampling with quick return of cross sectional area data.
Because of the irregular shape, accurate cross sectional area measurement is complicated. Existing methods require the sample to be cooled, cut to an accurate length with clean faces using a cold saw, and weighed on an accurate balance scale. Using the known density of steel and known length, cross section is calculated and plotted for statistical purposes. The process is tedious and prone to inaccuracy.
Other approaches of the prior art are illustrated in U.S. Pat. Nos. 3,851,180, Kato et al, Nov. 26, 1974 and 3,709,610, Kruegle, Jan. 9, 1973.
The '180 patent uses a laser arrangement to measure the diameter of the fine wire by counting the spacing between bright spots of a Fraunhofer diffraction image formed by irradiating the fine wire with parallel laser light beams.
The '610 patent uses the same approach and measures the spacing between light and dark portions of the diffraction pattern.
Although the diameter of the fine wire is determined using the patented apparatus, unless we assume a circular shape, neither the shape nor the cross sectional area is determined using these approaches.